Highly Efficient, Incoherent Slab-Pumped Fiber Amplifier/Laser Designs

摘要

The problem of delivering a multimode pump to a single mode core is considered. Original designs of double-clad fiber amplifiers are analyzed. A slab pump geometry of a fiber amplifier is suggested. The partially coherent pump should be coupled to the narrow slab which supports propagation of the pump and absorbs highest modes of the core, then the core itself has no need to be single-mode. The slab plays the role of cladding in conventional double-clad fibers. Such a cladding has no need to surround the core and its refractive index can be higher than that of the core. Then the highest modes of the slab are absorbed at very beginning of the amplifier. This allows for tapering of the slab, providing almost constant pump power in the core. The end result is a the high efficiency of a compact device with scaling to high pump power. We provide the key design formulas for such a device.